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Obstetrics and Periodontal Therapy Dataset

Source: R/opt.R
opt.Rd

The objective of this randomized controlled trial was to determine whether treatment of maternal periodontal disease can reduce risk of preterm birth and low birth weight (more details available below the variable definitions).

Usage

opt

Format

A data frame with 823 observations and 171 variables

PID

Participant ID, First digit indicates enrollment center (1 = NY, 2 = MN, 3 = KY, 4 = MS); Next 4 digits are sequential; Sixth digit is a check digit; There are no missing data, numeric, range: 100034-402477

Clinic

Enrollment Center, factor, NY = Harlem Hospital, MN = Hennepin County Center; KY = University of Kentucky; MS = University of Mississippi Medical Center; There are no missing data

Group

Randomized treatment assignment, factor, T = Intervention; C = Control; There are no missing data

Age

Age of participant at baseline (years), numeric, range: 16-44

Black

Black participant (self-identified), factor; Yes, No

White

White participant (self-identified), factor; Yes, No

Nat.Am

Native American participant, incl. Latin Americans with aboriginal origin(self-identified), factor; Yes, No

Asian

Asian participant (self-identified), factor; Yes, No

Hisp

Hispanic participant (self-identified), factor; Yes, No

Education

Education level of participant, factor; LT 8 yrs = Less than 8 years; 8-12 yrs = 8 to 12 years; MT 12 yrs = More than 12 yrs; blank = Missing

Public.Asstce

Public Assistance: Whether a government agency paid for the delivery, factor; Yes, No;

Hypertension

Whether participant had chronic hypertension at baseline, factor; Yes, No

Diabetes

Whether participant had diabetes at baseline (self-reported), factor; Yes, No

BL.Diab.Type

Baseline Diabetes Type: Type of diabetes, for participants having diabetes at baseline (self-reported), factor; Type I; Type II; Blank = No diabetes at baseline (variable 13 = No)

BMI

NA, numeric, range: 15.000-68.0

Use.Tob

Self-reported participant history of tobacco use, factor; Yes, No; Blank = Missing

BL.Cig.Day

Self-reported number of cigarettes per day for those with tobacco use history, numeric, range: 1-30; Blank = Missing (variable 16= Yes or blank) or non-smoker (variable 16 = No)

Use.Alc

Self-reported participant history of alcohol use, factor; Yes, No; Blank = Missing

BL.Drks.Day

, Blank = Missing (variable 18 = Yes or blank) or non-drinker (variable 18 = No)

Drug.Add

Self-reported participant history of drug addiction, factor; Yes, No; Blank = Missing

Prev.preg

Any previous pregnancy, factor; Yes, No; No missing data

N.prev.preg

Number of previous pregnancies for those with any previous pregnancy, numeric, range: 1-11; Blank = Missing (variable 21 = Yes) or no previous pregnancies (variable 21 = No)

Live.PTB

Previous live preterm birth for those with any previous pregnancy, factor; Yes; No = No previous live preterm birth (variable 21 = Yes) or no previous pregnancies (variable 21 = No)

Any.stillbirth

Previous stillbirth, factor; Yes; No = No previous stillbirth (variable 21 = Yes) or no previous pregnancies (variable 21 = No)

Spont.ab

Previous spontaneous abortion, factor; Yes; No; Blank = Missing (variable 21 = Yes) or no previous pregnancies (variable 21 = No)

Induced.ab

Previous induced abortion, factor; Yes; No; Blank = Missing (variable 21 = Yes) or no previous pregnancies (variable 21 = No)

Any.live.ptb.sb.sp.ab.in.ab

Any previous live pre-term birth, stillbirth, spontaneous abortion, or induced abortion, factor; Yes; No = No live pre-term birth/stillbirth/abortion (variable 21 = Yes) or no previous pregnancies (variable 21 = No)

N.living.kids

Number of living children the subject had at baseline, numeric, range: 0-9; Blank = Missing (variable 21 = Yes) or no previous pregnancies (variable 21 = No)

Tx.comp.

Whether treatment plans were completed by participants in treatment group, factor, Yes = Completed; No = Not completed; Und = Some therapy (unknown whether completed); Blank = Withdrew from treatment (variable 3 = T) or no periodontal therapy (variable 3 = C)

Local.anes

Whether any local anesthetic used during periodontal therapy for participants in treatment group, factor, Yes; No = No local anesthetic used or withdrew from treatment (variable 3 = T); Blank = No periodontal therapy (variable 3 = C)

Topical.Anest

Whether any topical anesthetic used during periodontal therapy for participants in treatment group, factor, Yes; No = No topical anesthetic used or withdrew from treatment (variable 3 = T); Blank = No periodontal therapy (variable 3 = C)

Tx.time

Total treatment time for participants in treatment group (hours), numeric, range: 0.117-5.8; Blank = Withdrew from treatment (variable 3 = T and variable 29 = blank) or no periodontal therapy (variable 3 = C)

EDC.necessary.

Whether patient required1 essential dental care (EDC), factor, Yes; No; Blank = Missing

Completed.EDC

Did patient complete EDC before 20 weeks gestational age?, factor, Yes; No; Blank = Missing

N.extractions

Number of teeth extracted during EDC, numeric, range: 0-20; Blank = Missing

N.perm.restorations

Number of permanent restorations carried out as a part of EDC, numeric, range: 0-18; Blank = Missing

N.qualifying.teeth

Number of teeth meeting OPT (Obstetrics and Periodontal Therapy Study) criteria for having periodontal disease at baseline, numeric, range: 3.000-28.0

BL.GE

Whole-mouth average gingival index at baseline, numeric, range: 0.429-3.0, Silness-Lowe Gingival Index: Higher value indicates more severe inflammation; 0 = Normal gingiva; There are no missing data

BL..BOP

Percentage of sites bleeding on probing at baseline, numeric, range:33.951-100.0

BL.PD.avg

Whole-mouth average pocket depth at baseline (mm), numeric, range: 1.851-7.0

BL..PD.4

Percentage of sites with pocket depth greater than or equal to 4mm at baseline, numeric, range: 3.571-99.2

BL..PD.5

Percentage of sites with pocket depth greater than or equal to 5mm at baseline, numeric, range: 0-91.7

BL.CAL.avg

Whole-mouth average clinical attachment level at baseline (mm), numeric, range: 0.185-5.1

BL..CAL.2

Percentage of sites with clinical attachment level greater than or equal to 2 mm at baseline, numeric, range: 2.381-100.0

BL..CAL.3

Percentage of site with clinical attachment level greater than or equal to 3 mm at baseline, numeric, range: 0-94.9

BL.Calc.I

Whole-mouth average calculus index at baseline, Simplified Oral Hygiene Index (OHI-S): Higher value indicates more calculus; 0 = No calculus present; numeric, range: 0-3.0

BL.Pl.I

Whole-mouth average plaque index at baseline, Silness-Lowe Gingival Index:Higher value indicates more severe inflammation, 0= normal gingiva, numeric, range: 0.056-3.0

V3.GE

Whole-mouth average gingival index at Visit 3, numeric, range: 0.030-3.0

V3..BOP

Percentage of sites bleeding on probing at Visit 3, numeric, range: 0.725-100.0, Blank = Missing

V3.PD.avg

Whole-mouth average pocket depth at Visit 3 (mm), numeric, range: 1.601-5.5, Blank = Missing

V3..PD.4

Percentage of sites with pocket depth greater than or equal to 4mm at Visit 3, numeric, range: 0-83.9, Blank = Missing

V3..PD.5

Percentage of sites with pocket depth greater than or equal to 5mm at Visit 3, numeric, range: 0-77.4, Blank = Missing

V3.CAL.avg

Whole-mouth average clinical attachment level at Visit 3 (mm), numeric, range: 0.036-3.9, Blank = Missing

V3..CAL.2

Percentage of sites with clinical attachment level greater than or equal to 2 mm at visit 3, numeric, range: 0-97.8, Blank = Missing

V3..CAL.3

Percentage of sites with clinical attachment level greater than or equal to 3 mm at visit 3, numeric, range: 0-85.7, Blank = Missing

V3.Calc.I

Whole-mouth average calculus index at visit 3, numeric, range: 0-2.6, Simplified Oral Hygiene Index (OHI-S): Higher value indicates more calculus; 0 = No calculus present; Blank = Missing

V3.Pl.I

Whole-mouth average plaque index at visit 3, numeric, range: 0-2.6, Silness-Lowe Plaque Index: Higher value indicates more abundant plaque; 0 = No plaque in gingival area; Blank = Missing

V5.GE

Whole-mouth average gingival index at visit 5, numeric, range: 0.190-2.7, Silness-Lowe Gingival Index: Higher value indicates more severe inflammation; 0 = Normal gingiva; Blank = Missing

V5..BOP

Percentage of sites bleeding on probing at visit 5, numeric, range: 3.571-100.0, Blank = Missing

V5.PD.avg

Whole-mouth average pocket depth at visit 5, numeric, range: 1.536-5.4, Blank = Missing

V5..PD.4

Percentage of sites with pocket depth greater than or equal to 4mm at Visit 5, numeric, range: 0-83, Blank = Missing

V5..PD.5

Percentage of sites with pocket depth greater than or equal to 5mm at Visit 3, numeric, range: 0-75.6, Blank = Missing

V5.CAL.avg

Whole-mouth average clinical attachment level at visit 5 (mm), numeric, range: 0.018-4.3, Blank = Missing

V5..CAL.2

Percentage of sites with clinical attachment level greater than or equal to 2 mm at visit 5, numeric, range: 0.000-99.2, Blank = Missing

V5..CAL.3

Percentage of sites with clinical attachment level greater than or equal to 3 mm at visit 5, numeric, range: 0.000-85.0, Blank = Missing

V5.Calc.I

Whole-mouth average calculus index at visit 5, numeric, range: 0.0-2.6, Simplified Oral Hygiene Index (OHI-S): Higher value indicates more calculus; 0 = No calculus present; Blank = Missing

V5.Pl.I

Whole-mouth average plaque index at visit 5, numeric, range: 0.0-2.5, Silness-Lowe Plaque Index: Higher value indicates more abundant plaque; 0 = No plaque in gingival area; Blank = Missing

N.PAL.sites

Number of sites for which attachment loss increased from baseline by greater than or equal to 3 mm, numeric, range: 0-33, 0 = No sites; Blank = Missing

Birth.outcome

Birth outcome, factor, Elective abortion; Live birth; Lost to FU = Lost to Follow-Up; Non-live birth = Stillbirth or spontaneous abortion; There are no missing data

Preg.ended...37.wk

Whether the pregnancy ended before gestational age 37 weeks (259 days), factor, Yes; No; Blank = Lost to Follow-Up

GA.at.outcome

Gestational age at end of pregnancy, or at mother's last follow-up visit if lost to follow-up, numeric, range: 103-302

Birthweight

Infant birth weight at time of birth, abstracted from obstetrical records (grams), numeric, range: 101-5160, Blank = Missing

Fetal.congenital.anomaly

Fetal/congenital anomaly identified at birth or during pregnancy?, factor, Yes; No; There are no missing data

Apgar1

Apgar score, a summary of a newborn infant's 'Appearance, Pulse, Grimace, Activity, Respiration' at 1 minute Score interpretation: less than or equal to 3: Critically low 4-6: Fairly low greater than or equal to 7: Normal, numeric, range: 0-10, Blank = Missing

Apgar5

Apgar score at 5 minutes, numeric, range: 0-10, Blank = Missing

Any.SAE.

Whether participant experienced any serious adverse events (e.g. lost pregnancies) factor, Yes; No; There are no missing data

GA...1st.SAE

Gestational age of first SAE (serious adverse event), integer, range: 96-467, 259 = No SAE (variable 76 must = No); There are no missing data

Bact.vag

Whether mother had bacterial vaginosis during pregnancy, factor, Yes; No; Blank = Missing

Gest.diab

Whether mother had gestational diabetes during pregnancy, factor, Yes; No; Blank = Missing

Oligo

Whether mother had oligohydramnios during pregnancy, factor, Yes; No; Blank = Missing

Polyhyd

Whether mother had polyhydramnios during pregnancy, factor, Yes; No; Blank = Missing

Gonorrhea

Whether mother had gonorrhea during pregnancy, factor, Yes; No; Blank = Missing

Chlamydia

Whether mother had chlamydia during pregnancy, factor, Yes; No; Blank = Missing

Strep.B

Whether mother had strep B colonization during pregnancy, factor, Yes; No; Blank = Missing

Traumatic.Inj

Whether mother had a traumatic injury during pregnancy, factor, Yes; No; Blank = Missing

UTI

Whether mother had a urinary tract infection during pregnancy, factor, Yes; No; Blank = Missing

Pre.eclamp

Whether mother had pre-eclampsia, a pregnancy condition characterized by high blood pressure and associated with fetal growth restriction during pregnancy, factor, Yes; No; Blank = Missing

Mom.HIV.status

HIV status of mother during pregnancy, factor, Yes = HIV-positive; No = HIV-negative or unknown (question answered but HIV status at delivery not recorded); Blank = Missing (question not answered)

BL.Anti.inf

Did participant report use of antiinflammatory medication at or less than 6 months before baseline?, integer, 0 = No; 1 = Yes; There are no missing data

BL.Cortico

Did participant report use of corticosteroids at or less than 6 months before baseline?, integer, 0 = No; 1 = Yes; There are no missing data

BL.Antibio

Did participant report use of antibiotics at or less than 6 months before baseline?, integer, 0 = No; 1 = Yes; There are no missing data

BL.Bac.vag

Did participant report use of bacterial vaginitis treatments at or less than 6 months before baseline?, integer, 0 = No; 1 = Yes; There are no missing data

V3.Anti.inf

Did participant report use of antiinflammatory medication between baseline and visit 3?,integer, 0 = No; 1 = Yes; There are no missing data

V3.Cortico

Did participant report use of corticosteroids between baseline and visit 3?, integer, 0 = No; 1 = Yes; There are no missing data

V3.Antibio

Did participant report use of antibiotics between baseline and visit 3?, integer, 0 = No; 1 = Yes; There are no missing data

V3.Bac.vag

Did participant report use of bacterial vaginitis treatments between baseline and visit 3?, integer, 0 = No; 1 = Yes; There are no missing data

V5.Anti.inf

Did participant report use of antiinflammatory medication between visit 3 and visit 5?, integer, 0 = No; 1 = Yes; There are no missing data

V5.Cortico

Did participant report use of corticosteroids between visit 3 and visit 5?, integer, 0 = No; 1 = Yes; There are no missing data

V5.Antibio

Did participant report use of antibiotics between visit 3 and visit 5?, integer, 0 = No; 1 = Yes; There are no missing data

V5.Bac.vag

Did participant report use of bacterial vaginitis treatments between visit 3 and visit 5?, integer, 0 = No; 1 = Yes; There are no missing data

X..Vis.Att

Visit attendance: Number of study visits attended AFTER baseline, integer, Range: 0-5

X..Vis.Elig

Number of visits for which participant was eligible (could become ineligible after miscarriage or early delivery), integer, Range: 0-5

X1st.Miss.Vis

First missed visit. No one missed the baseline visit, so this variable takes values 2, 3, 4, 5, 6, and 100 (no eligible visits missed), integer, Range: 2-6, 100

OAA1

Serum IgG (immunoglobulin) antibodies to A. actinomycetemcomitans at baseline, factor (actually numeric or missing), dot(.) = Missing

OCR1

Serum IgG (immunoglobulin) antibodies to C. rectus at baseline, factor (actually numeric or missing), dot(.) = Missing

OFN1

Serum IgG (immunoglobulin) antibodies to F. nucleatum at baseline, factor (actually numeric or missing), dot(.) = Missing

OPG1

Serum IgG (immunoglobulin) antibodies to P. gingivalis at baseline, factor (actually numeric or missing), dot(.) = Missing

OPI1

Serum IgG (immunoglobulin) antibodies to P. intermedia at baseline, factor (actually numeric or missing), dot(.) = Missing

OTD1

Serum IgG (immunoglobulin) antibodies to T. denticola at baseline, factor (actually numeric or missing), dot(.) = Missing

OTF1

Serum IgG (immunoglobulin) antibodies to T. forsythus at baseline, factor (actually numeric or missing), dot(.) = Missing

OCRP1

Serum measure for C-reactive protein (CRP) at baseline, factor (actually numeric or missing), dot(.) = Missing

O1B1

Serum measure for Interleukin(IL)-1b at baseline, factor (actually numeric or missing), dot(.) = Missing

O61

Serum measure for Interleukin(IL)-6 at baseline, factor (actually numeric or missing), dot(.) = Missing

O81

Serum measure forInterleukin(IL)-8 at baseline, factor (actually numeric or missing), dot(.) = Missing

OPGE21

Serum measure for Prostaglandin E2 at baseline, factor (actually numeric or missing), dot(.) = Missing

OTNF1

Serum measure for tumor necrosis factor (TNF)-alpha at baseline, factor (actually numeric or missing), dot(.) = Missing

OMMP91

Serum measure for gelatinase (MMP9) at baseline, factor (actually numeric or missing), dot(.) = Missing

ETXU_CAT1

Serum endotoxin level at baseline, factor (actually numeric or missing), dot(.) = Missing

OFIBRIN1

Serum measure for fibrinogen at baseline, factor (actually numeric or missing), dot(.) = Missing

OAA5

Serum IgG (immunoglobulin) antibodies to A. actinomycetemcomitans at visit 5, factor (actually numeric or missing), dot(.) = Missing

OCR5

Serum IgG (immunoglobulin) antibodies to C. rectus at visit 5, factor (actually numeric or missing), dot(.) = Missing

OFN5

Serum IgG (immunoglobulin) antibodies to F. nucleatum at visit 5, factor (actually numeric or missing), dot(.) = Missing

OPG5

Serum IgG (immunoglobulin) antibodies to P. gingivalis at visit 5, factor (actually numeric or missing), dot(.) = Missing

OPI5

Serum IgG (immunoglobulin) antibodies to P. intermedia at visit 5, factor (actually numeric or missing), dot(.) = Missing

OTD5

Serum IgG (immunoglobulin) antibodies to T. denticola at visit 5, factor (actually numeric or missing), dot(.) = Missing

OTF5

Serum IgG (immunoglobulin) antibodies to T. forsythus at visit 5, factor (actually numeric or missing), dot(.) = Missing

OCRP5

Serum measure for C-reactive protein (CRP) at visit 5, factor (actually numeric or missing), dot(.) = Missing

O1B5

Serum measure for Interleukin(IL)-1b at visit 5, factor (actually numeric or missing), dot(.) = Missing

O65

Serum measure forInterleukin(IL)-6 at visit 5, factor (actually numeric or missing), dot(.) = Missing

O85

Serum measure forInterleukin(IL)-8 at visit 5, factor (actually numeric or missing), dot(.) = Missing

OPGE25

Serum measure for Prostaglandin E2 at visit 5, factor (actually numeric or missing), dot(.) = Missing

OTNF5

Serum measure for tumor necrosis factor (TNF)-alpha at visit 5, factor (actually numeric or missing), dot(.) = Missing

OMMP95

Serum measure for gelatinase (MMP9) at visit 5, factor (actually numeric or missing), dot(.) = Missing

ETXU_CAT5

Serum endotoxin level at visit 5, factor (actually numeric or missing), dot(.) = Missing

OFIBRIN5

Serum measure for fibrinogen at visit 5, factor (actually numeric or missing), dot(.) = Missing

BL.DNA

Total amount of bacterial DNA extracted from plaque as a measure of total bacterial concentration at baseline (ng/mL), numeric, range: 0-5750.0

BL.Univ

Count of all bacteria detected by universal primer at baseline, numeric, range: 1,890,000-1,070,000,000, Blank = Missing

BL.AA

Count of A. actinomycetemcomitans bacteria at baseline, numeric, range: 0-7,970,000, Blank = Missing

BL.PG

Count of P. gingivalis bacteria at baseline, numeric, range: 0-167,000,000, Blank = Missing

BL.TD

Count of T. denticola bacteria at baseline, numeric, range: 0-50,500,000, Blank = Missing

BL.TF

Count of T. forsythus bacteria at baseline, numeric, range: 0-40,200,000, Blank = Missing

BL.PI

Count of P. intermedia bacteria at baseline, numeric, range: 0-87,500,000, Blank = Missing

BL.CR

Count of C. rectus bacteria at baseline, numeric, range: 0-32,600,000, Blank = Missing

BL.FN

Count of F. nucleatum bacteria at baseline, numeric, range: 67,300- 152,000,000, Blank = Missing

BL.S7

Sum of the 7 species-specific bacterial counts (variables 138-144) at baseline, rounded to 3 significant figures, numeric, range: 87,000-391,000,000, Blank = Missing

V5.DNA

Total amount of bacterial DNA extracted from plaque as a measure of total bacterial concentration at visit 5 (ng/mL), numeric, range: 0-5750.0

V5.Univ

Count of all bacteria detected by universal primer at visit 5, numeric, range: 1,890,000-1,070,000,000, Blank = Missing

V5.AA

Count of A. actinomycetemcomitans bacteria at visit 5, numeric, range: 0-40,200,000, Blank = Missing

V5.PG

Count of P. gingivalis bacteria at visit 5, numeric, range: 0-40,200,000, Blank = Missing

V5.TD

Count of T. forsythus bacteria at visit 5, numeric, range: 0-40,200,000, Blank = Missing

V5.TF

Count of T. forsythus bacteria at visit 5, numeric, range: 0-40,200,000, Blank = Missing

V5.PI

Count of P. intermedia bacteria at visit 5, numeric, range: 0-87,500,000, Blank = Missing

V5.CR

Count of C. rectus bacteria at visit 5, numeric, range: 0-32,600,000, Blank = Missing

V5.FN

Count of F. nucleatum bacteria at visit 5, numeric, range: 67,300- 152,000,000, Blank = Missing

V5.S7

Sum of the 7 species-specific bacterial counts (variables 138-144) at visit 5, rounded to 3 significant figures, numeric, range: 87,000-391,000,000, Blank = Missing

BL..AA

Percent of A. actinomycetemcomitans out of total DNA (variable 146) at baseline, numeric, range: 0-8.9, Blank = Missing

BL..PG

Percent of P. gingivalis out of total DNA at baseline, numeric, range: 0-37.3, Blank = Missing

BL..TD

Percent of T. denticola out of total DNA at baseline, numeric, range: 0-13.2, Blank = Missing

BL..TF

Percent of T. forsythus out of total DNA at baseline, numeric, range: 0-17.7, Blank = Missing

BL..PI

Percent of P. intermedia out of total DNA at baseline, numeric, range: 0-46.3, Blank = Missing

BL..CR

Percent of C. rectus out of total DNA at baseline, numeric, range: 0-10.5, Blank = Missing

BL..FN

Percent of F. nucleatum out of total DNA at baseline, numeric, range: 0.330-63.2, Blank = Missing

BL..S7

Sum of the percents for the 7 species (AA, PG, TD, TF, PI, CR, and FN) at baseline, numeric, range: 0.420-86.3, Blank = Missing

V5..AA

Percent of A. actinomycetemcomitans out of total DNA at visit 5, numeric, range: 0-16.1, Blank = Missing

V5..PG

Percent of P. gingivalis out of total DNA at visit 5, numeric, range: 0-59.7, Blank = Missing

V5..TD

Percent of T. denticola out of total DNA at visit 5, numeric, range: 0-20.5, Blank = Missing

V5..TF

Percent of T. forsythus out of total DNA at visit 5, numeric, range: 0-19.3, Blank = Missing

V5..PI

Percent of P. intermedia out of total DNA at visit 5, numeric, range: 0-40.7, Blank = Missing

V5..CR

Percent of C. rectus out of total DNA at visit 5, numeric, range: 0-14.6, Blank = Missing

V5..FN

Percent of F. nucleatum out of total DNA at visit 5, numeric, range: 0-49.9, Blank = Missing

V5..S7

Sum of the percents for the 7 species (AA, PG, TD, TF, PI, CR, and FN) at visit 5, numeric, range: 2.560-80.8, Blank = Missing

Source

Michalowicz et al., 'Treatment of periodontal disease and the risk of preterm birth', N Engl J Med 2006; 355:1885-1894. DOI: 10.1056/NEJMoa062249

Details

Background:

Randomized Clinical Trial on the Effect of Treatment of Maternal Periodontal Disease Can Reduce Preterm Birth Risk.
Maternal periodontal disease has been linked in observational studies to preterm birth (< 37 weeks) and low birth weight (< 2500 g) outcomes. The Obstetrics and Periodontal Therapy study was a multi-center randomized trial evaluating the effect of nonsurgical periodontal treatment intervention on preterm birth, comparing outcomes of women treated before 21 weeks gestation (treatment) to those treated after delivery (control).
Preterm birth, defined as delivery before 37 weeks of gestation, is a growing problem. In some cases, preterm birth can lead to infant death; in others, its consequences may include neurodevelopmental disabilities, cognitive impairment, and/or respiratory disorders in the child. Many risk factors for preterm birth have already been identified, including maternal age, drug use, and diabetes. However, such factors are exhibited in only about half of preterm birth mothers, highlighting a need to expand our understanding of what contributes to preterm birth risk.
Several observational studies have suggested an association between maternal periodontal disease and preterm birth. Periodontal disease is an inflammatory condition characterized by the destruction of tissue and/or bone around the teeth. A major component of periodontal disease is oral colonization by gram-negative bacteria; systemic release of cytokines and/or lipopolysaccharides from these bacteria may impact fetal condition.
Inoculation of the periodontal pathogen P. gingivalis into pregnant animals does have a dose-dependent effect on birth weight and preterm birth signaling, but no such causal link has been shown in humans, only some associations. Though not definitive, the possibility of a significant relationship raises the question of whether treatment of maternal periodontal disease can decrease preterm birth risk.

Participants:

823 participants enrolled at 4 centers underwent stratified randomization, resulting in 413 women assigned to the treatment group and 410 to control. All participants were 13-16 weeks pregnant at time of randomization (baseline/visit 1) and went on to attend monthly follow-up visits defined as visits 2, 3, 4, and 5 corresponding to gestational age ranges of 17-20, 21-24, 25-28, and 29-32 weeks.

Treatment:

The treatment group received periodontal treatment, oral hygiene instruction, and tooth polishing at their follow-ups, while those assigned to control underwent only brief oral exams. Data collection occurred at visits 1 (baseline), 3, and 5. The primary outcome of interest is gestational age at end of pregnancy. Additional outcomes include birthweight, clinical measures of periodontal disease, and various microbiological and immunological outcomes.

Analysis:

Statistical analyses were carried out on an intent-to-treat basis. Gestational age can be thought of as 'time until end of pregnancy,' for which certain survival analysis methods would be appropriate. The study used a log-rank test stratified by center to compare time until end of pregnancy for treatment and control groups.
A semiparametric proportional hazards model was also used for this purpose and incorporated maternal risk factors as predictors. For the study's main analyses, gestational age was censored at 37 weeks (259 days) because the interest was in extending pregnancies that would otherwise end pre-term, not extending pregnancies generally.
Though not used in the study itself, logistic regression is another method that could be applied: for example, to gestational age, dichotomized as 'preterm' or 'not preterm' according to a gestational age cutoff, or to birthweight dichotomized as 'low' or 'high' at the 2500 g or other cutoff (2500 g would be in keeping with the World Health Organization's definition for low birth weight). Changes in clinical measures of periodontal disease from baseline to visits 3 or 5 could be analyzed using mixed effects linear models. The dataset also features a number of baseline characteristics, which could be compared in treatment and control groups via Student t-tests, Wilcoxon rank sum tests, Fisher's exact tests or Pearson's chi-square tests, as appropriate.

Publishing:

The nonsurgical periodontal treatment involving scaling and root planing induced significant improvements in periodontal health. The study did not however find a significant relation between periodontal treatment and preterm birth risk. The results of this study were published in 2006 by Michalowicz et al., 'Treatment of periodontal disease and the risk of preterm birth', in The New England Journal of Medicine. The Obstetrics and Periodontal Therapy Dataset contains the data used in this study.
The obstetrics and periodontal therapy dataset was contributed by Dr. Ann Brearley, Assistant Professor, Division of Biostatistics, School of Public Health, University of Minnesota and her colleagues. Please refer to this resource as: Meredith Hyun, James S. Hodges and Ann M. Brearley, 'Obstetrics and Periodontal Therapy Dataset', TSHS Resources Portal (2019). Available at https://www.causeweb.org/tshs/obstetrics-and-periodontal-therapy/.